attempt to put a process's cwd back in place after a forced umount.

won't always work, but it's the best we can do for now.  this covers
at least some of the failure cases the previous commit to vfs_lookup.c
checks for.
ok weingart@

3 files changed, 37 insertions, 8 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index b4192a84ee9..6d30d424d67 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vfs_subr.c,v 1.90 2003/05/01 21:13:05 tedu Exp $	*/
+/*	$OpenBSD: vfs_subr.c,v 1.91 2003/05/06 20:52:14 tedu Exp $	*/
 /*	$NetBSD: vfs_subr.c,v 1.53 1996/04/22 01:39:13 christos Exp $	*/
 
 /*
@@ -1771,7 +1771,7 @@ vfs_unmountall(void)
 		nmp = CIRCLEQ_PREV(mp, mnt_list);
 		if ((vfs_busy(mp, LK_EXCLUSIVE|LK_NOWAIT, NULL, p)) != 0)
 			continue;
-		if ((error = dounmount(mp, MNT_FORCE, curproc)) != 0) {
+		if ((error = dounmount(mp, MNT_FORCE, curproc, NULL)) != 0) {
 			printf("unmount of %s failed with error %d\n",
 			    mp->mnt_stat.f_mntonname, error);
 			allerror = 1;
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index d9283e3445e..016dbefd8e8 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vfs_syscalls.c,v 1.102 2003/05/05 00:21:52 tedu Exp $	*/
+/*	$OpenBSD: vfs_syscalls.c,v 1.103 2003/05/06 20:52:14 tedu Exp $	*/
 /*	$NetBSD: vfs_syscalls.c,v 1.71 1996/04/23 10:29:02 mycroft Exp $	*/
 
 /*
@@ -426,16 +426,17 @@ sys_unmount(p, v, retval)
 	if (vfs_busy(mp, LK_EXCLUSIVE, NULL, p))
 		return (EBUSY);
 
-	return (dounmount(mp, SCARG(uap, flags), p));
+	return (dounmount(mp, SCARG(uap, flags), p, vp));
 }
 
 /*
  * Do the actual file system unmount.
  */
 int
-dounmount(struct mount *mp, int flags, struct proc *p)
+dounmount(struct mount *mp, int flags, struct proc *p, struct vnode *olddp)
 {
 	struct vnode *coveredvp;
+	struct proc *p2;
 	int error;
 	int hadsyncer = 0;
 
@@ -460,7 +461,30 @@ dounmount(struct mount *mp, int flags, struct proc *p)
 	}
 	CIRCLEQ_REMOVE(&mountlist, mp, mnt_list);
 	if ((coveredvp = mp->mnt_vnodecovered) != NULLVP) {
-		coveredvp->v_mountedhere = (struct mount *)0;
+		if (olddp) {
+			/* 
+			 * Try to put processes back in a real directory
+			 * after a forced unmount.
+			 * XXX We're not holding a ref on olddp, which may
+			 * change, so compare id numbers.
+			 */
+			LIST_FOREACH(p2, &allproc, p_list) {
+				struct filedesc *fdp = p2->p_fd;
+				if (fdp->fd_cdir &&
+				    fdp->fd_cdir->v_id == olddp->v_id) {
+					vrele(fdp->fd_cdir);
+					vref(coveredvp);
+					fdp->fd_cdir = coveredvp;
+				}
+				if (fdp->fd_rdir &&
+				    fdp->fd_rdir->v_id == olddp->v_id) {
+					vrele(fdp->fd_rdir);
+					vref(coveredvp);
+					fdp->fd_rdir = coveredvp;
+				}
+			}
+		}
+		coveredvp->v_mountedhere = NULL;
  		vrele(coveredvp);
  	}
 	mp->mnt_vfc->vfc_refcount--;
diff --git a/sys/ufs/mfs/mfs_vfsops.c b/sys/ufs/mfs/mfs_vfsops.c
index e9e6a7013e8..f02d061e52d 100644
--- a/sys/ufs/mfs/mfs_vfsops.c
+++ b/sys/ufs/mfs/mfs_vfsops.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mfs_vfsops.c,v 1.22 2002/07/12 14:02:23 art Exp $	*/
+/*	$OpenBSD: mfs_vfsops.c,v 1.23 2003/05/06 20:52:14 tedu Exp $	*/
 /*	$NetBSD: mfs_vfsops.c,v 1.10 1996/02/09 22:31:28 christos Exp $	*/
 
 /*
@@ -259,6 +259,7 @@ mfs_start(mp, flags, p)
 	struct proc *p;
 {
 	struct vnode *vp = VFSTOUFS(mp)->um_devvp;
+	struct vnode *rvp;
 	struct mfsnode *mfsp = VTOMFS(vp);
 	struct buf *bp;
 	caddr_t base;
@@ -278,8 +279,12 @@ mfs_start(mp, flags, p)
 		 * EINTR/ERESTART.
 		 */
 		if (sleepreturn != 0) {
+			if (ufs_root(mp, &rvp))
+				rvp = NULL;
+			else
+				vput(rvp);
 			if (vfs_busy(mp, LK_EXCLUSIVE|LK_NOWAIT, NULL, p) ||
-			    dounmount(mp, 0, p))
+			    dounmount(mp, 0, p, rvp))
 				CLRSIG(p, CURSIG(p));
 			sleepreturn = 0;
 			continue;